Clinical and radiological investigations were performed for 2,258 aluminum workers exposed to fluoride for an average of 17.6 yr (standard deviation = 7.6). Changes in bone and joints were presented in detail in three groups: (1) exposed up to 5 yr (135 cases), (2) exposed from 6-32 yr (1,463 cases), and (3) retired workers (660 cases). A semiquantitative assessment of early fluorosis was introduced. A 20.2% incidence of fluorosis was found, but, according to Roholm, only 1.05% was in stage I. The disease was mainly in the pre-stages of O and OI. A close relationship between the occurrence of fluorosis and the time and degree of fluoride exposure was found. The difficulties in diagnosing skeletal fluorosis result from the questionable sensitivity of the x-ray techniques and from the nonspecificity of the associated symptoms. A quantitative method to assess osteosclerosis and bone structure alteration is needed.